Answer:
22.5
Step-by-step explanation:
If you expand the series, you can see the first few terms of the series:
- Putting 1 in
, 
- Putting 2 in
, 
- Putting 3 in
,
- Putting 4 in
,
We can see the series is 0, 0.5, 1, 1.5, ....
This is an arithmetic series with common difference (the difference in 2 terms) 0.5 and first term 0.
We know formula for sum of arithmetic series:

Where,
denotes the nth partial sum
is the first term (in our case it is 0)
is the term (in our case it is 10 since we want to find 10th partial sum -- sum until first 10 terms)
is the common difference (difference in term and the previous term) (in our case it is 0.5)
Substituting these into the formula, we get the 10th partial sum to be:

So the sum of the first 10 terms is 22.5. Third answer choice is right.
D. Subtract 2 from the number of sides and multiply the difference by 180
Answer:
x = 2
y = 0
Step-by-step explanation:
We can solve using substitution, substitute y in the first equation with the second equation:
-(-6x + 12) + 3x = 6
Distribute the negative sign:
6x - 12 + 3x = 6
Combine like terms:
9x - 12 = 6
Isolate the variable and solve for x by adding 12 in both sides:
9x = 18
x = 2
Substitute 2 with x in any equation to find the value of y:
-y + 3(2) = 6
-y + 6 = 6
Subtract 6 in both sides to isolate the variable:
-y = 0
0/-1 = 0
y = 0
Our answer would be x = 2 and y = 0
Answer:
-12
Step-by-step explanation:
4 time 3 is 12
since he owes her its negative, so it is -12

From any proportion, we get another proportion by inverting the extremes (or the means):

= k
so we have:
2x=3k
2x+y=2k therefore:
3k+y=2k
y= - k
x=


= -

The corect answer is A. -3/2
or:

From any proportion, we get another proportion by inverting the extremes and the means:

We use a property of proportions:

where a, d are extremes and b,c are means and the product of the extremes equals the product of the means (a*d=b*c),
so we have

or

(you can check this also by "the product of the extremes equals the product of the means")



3y = - 2x